Therapeutic approach in Class I malocclusion with impacted maxillary canines

ABSTRACT Objective: To emphasize the importance of diagnosis and discuss the therapeutic approaches that can be used in the orthodontic treatment of Class I malocclusion associated with two impacted maxillary canines. The opening of spaces for traction of these teeth by means of rapid maxillary expansion or extraction of maxillary premolars was contraindicated in the case reported. Therefore, it was decided to open spaces with projection of incisors. Results: The obtained results were satisfactory, as a good occlusion was obtained, with adequate functional guides, as well as an improvement in the facial appearance. Conclusion: The projection of the incisors prior to traction of the impacted maxillary canines proved to be a valid option in the case described. Ten years after completion of treatment, the case is stable, maintaining periodontal health.


INTRODUCTION
Orthodontic traction of impacted canines is one of the greatest challenges in orthodontics. 1 It is a relatively frequent clinical condition (0.9 -2.2%), 2 and treatment sometimes should include a multidisciplinary approach. 3 Different etiologic factors are associated with impacted maxillary canines, such as ectopic location of the tooth germ, lack of space, lack of guidance, or genetic factors. 4 Surgical exposure of the impacted canine and complex orthodontic mechanics applied to align the tooth in the respective arch can often lead to supporting tissue complications, 5 in addition to a long treatment period and high costs for the patient. Therefore, early diagnosis is very important so that the problem can be managed as soon and efficiently as possible. 3 Before implementing any type of traction, it is important to create space for the impacted tooth. 6 This space can be created by maxillary expansion, 7 dental projection, 3 distalization of posterior teeth or extraction of permanent teeth adjacent to the impacted canine. The selection of the best treatment method rests upon correct diagnosis, to prevent adverse side effects. 8 When the chosen option is the projection of anterior teeth, one cannot rule out the possibility of orthodontic treatment promoting the development of gingival recessions 9,10 as orthodontic tooth movement could result in root positions that are close to or out of the cortical alveolar plates, leading to bone dehiscence. 11 As a result, a marginal gingiva without appropriate alveolar bone support can migrate apically, thus exposing the root. 12 The aim of the present study is to describe the orthodontic treatment of a Class I malocclusion associated with traction of two impacted canines for which the space created for their traction led to maxillary incisor proclination.

DIAGNOSIS
The patient, aged 18 years and 10 months, sought orthodontic treatment with the following complaint: "I have a milk tooth on one side, and on the other side, it goes inward into the arch." The patient's general health status was good, and her medical history was unremarkable; presenting good oral health and oral hygiene; presence of a deciduous tooth (deciduous maxillary right canine); and onychophagia. Prior to the treatment, a full orthodontic documentation and computed tomography were requested for assessment of the missing teeth (Fig 1).
The following facial features were observed: concave profile (upper lip-S line = -2 mm, lower lip-S line = -2 mm); passive lip seal; satisfactory nasolabial angle; short lower third of face; and unattractive gingival smile line, due to the presence of a deciduous tooth (deciduous maxillary right canine), missing teeth (permanent maxillary canines), and lingual crossbite (left maxillary lateral incisor). Clearly visible asymmetries were not detected. Malocclusion was classified as skeletal Class III (ANB = -10), with good relationship of the maxilla to the skull base and proclined mandible (SNA = 82º and SNB = 83º). There was balanced growth pattern, with horizontal facial growth tendency (SN.GoGn = 31º) (Figs 2, 3, 4 and 5).
Malocclusion was classified as Angle Class I, 3-mm overjet, and 4-mm severe overbite, mandibular anterior crowding, with arch length discrepancy of -3.7 mm; Bolton discrepancy of mandibular teeth, with excess of 0.3 mm in the anterior region; coincident midlines. The arches had a trapezoid shape and lacked space for maxillary canines, and left maxillary lateral incisor showed lingual crossbite (Figs 1 and 2).
The panoramic radiograph revealed the presence of all permanent teeth and one deciduous tooth (deciduous maxillary right canine), with mesially inclined impacted maxillary canines. Extensive restoration was observed on mandibular left first molar (Fig 3).
The periapical radiographs more clearly revealed the same findings as the panoramic radiograph. It was not possible, however, to assess the integrity of the maxillary lateral incisor roots, and a CT scan of the face was then requested. The CT scan revealed that the integrity of the maxillary lateral incisor roots was preserved, and that the right maxillary canine was located buccally to the right maxillary lateral incisor, whereas permanent maxillary left canine was located lingually to left maxillary lateral incisor (Figs 3 and 4).
In the functional evaluation, there was an absence of lateral guides in canines and of the anterior guide.  Extraction of maxillary deciduous right canine and intraoperative placement of the orthodontic device on the buccal aspect of maxillary right canine and maxillary left canine were requested (Fig 14).
Ten days after the surgical procedure, the patient came back to the Pithon MM -Therapeutic approach in Class I malocclusion with impacted maxillary canines              The skeletal relationship between the maxilla and the mandible was enhanced, probably due to repositioning of point A, with maintenance of horizontal growth pattern (Figs 24 and 25).
Class I molar relationship was maintained; crowding in both dental arches was corrected; space was created in the arch for canines; maxillary canines were subjected to traction; the mandibular premolars and molars were uprighted; and the mesiodistal Pithon MM -Therapeutic approach in Class I malocclusion with impacted maxillary canines

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Pithon MM -Therapeutic approach in Class I malocclusion with impacted maxillary canines Figure 29: Superimposed cephalometric tracings.

DISCUSSION
The permanent maxillary canines play a key role in shaping dentition and maintaining its function, and their presence in the dental arch is crucial for a balanced dynamic occlusion and for facial esthetics and harmony. [13][14][15] Thus, a great deal of effort should be expended to maintain or to avoid the extraction of an impacted permanent maxillary canine [16][17][18] . The present clinical case illustrates very well this scenario, with two impacted maxillary canines, one buccally inclined and one palatally inclined, which were moved into the spaces created orthodontically.
The maxillary canine is the most frequently impacted tooth, in a palatal to buccal impaction ratio of 3:1 to 6:1. 19 Girls are twice as often affected as boys, 20 and bilateral impaction occurs in only 8% of the cases. 21 The case described herein is therefore rare.
The first challenge in this case was the creation of enough space for the movement of canines. It has been widely described in the literature that creation of space is necessary prior to the orthodontic movement of any tooth. 6 In the case of impacted canines, the creation of space often occurs via arch expansion or extraction of premolars. 7 These approaches were not possible in the case described herein, as palatal disjunction was not indicated because the patient showed signs of calcification of the median palatine suture on the maxillary occlusal radiograph. Tooth extraction was also ruled out based on the patient's facial pattern and concave profile. Tooth extraction in this situation eventually increases concavity, making patients look older than they are. 22 Therefore, space was created by projecting the maxillary central incisors and extracting the right maxillary deciduous canine. The damage caused by tooth projection has been widely described in the literature. 23,24 However, in the present case, the retroclined incisors and the concave facial profile favored the decision to project the teeth, which allowed for a more harmonious profile at the end of the treatment.
Another challenge was the close relationship between the lateral incisor roots and unerupted canines. In the presence of impacted teeth, especially canines, it is always important to request a CT scan 6,25 to avoid surprises in the future.
The canines responded well to traction, which did not cause any damage to the roots of lateral incisors closely related to their crowns or damage to the periodontal tissues of canines, which displayed good gingival insertion at the end of the treatment. The decision not to align and level the maxillary lateral incisors at the beginning of treatment prevented their roots from being moved against the maxillary canines.
According to Yan et al., 26 physical proximity (< 1 mm) between the impacted canine and the adjacent root is the main predictor of root resorption. It should be highlighted that treatment of an impacted maxillary canine is not achieved exclusively by full orthodontic alignment. The final periodontal health is essential to assess the success of therapy, since biomechanical and surgical procedures can cause damage to the supporting tissues of the pulled and/or adjacent teeth. 27 Precaution was taken during treatment regarding the traction of palatally impacted canines by subjecting keratinized tissue to traction, which prevents gingival recession. 28 According to Ferreira et al., 16 knowledge of orthodontic mechanics is essential in cases of traction of impacted canines, and so is the management of applied forces.
Based on the records obtained at the end of the orthodontic treatment, it was possible to verify that all the proposed objectives were achieved. Class I relationship was obtained for molars and canines, satisfactory overjet and overbite, improvement in incisor inclination, alignment and leveling of all teeth, good periodontal health, intercuspation and adequate functional guides. The patient was satisfied with the results obtained mainly because she was informed at the beginning of the treatment that traction would be an attempt without guaranteed results.

CONCLUSION
In conclusion, the projection of incisors for space creation prior to the traction of impacted maxillary canines is a feasible treatment option when the incisors exhibit good periodontal health.
Patients displayed in this article previously approved the use of their facial and intraoral photographs.
The authors report no commercial, proprietary or financial interest in the products or companies described in this article.